1 Introduction
2 Materials and methods
2.1 Specimen configuration and assembly
Fungus/Condition | Screw on | Exposure time (weeks) | n | ρi (kg/m3) |
---|---|---|---|---|
Control (no sterilized, no fungus) | Face grain | 0 | 28 | 456 (35) |
End grain | 0 | 28 | 463 (35) | |
Sterilized (no fungus) | Face grain | 0 | 23 | 524 (34) |
25 | 10 | 512 (38) | ||
End grain | 0 | 10 | 505 (16) | |
25 | 10 | 453 (32) | ||
Fomitopsis ostreiformis (brown rot) | Face grain | 15 | 11 | 451 (48) |
20 | 12 | 447 (31) | ||
25 | 11 | 444 (46) | ||
End grain | 15 | 14 | 442 (18) | |
20 | 14 | 468 (38) | ||
25 | 20 | 441 (23) | ||
Pycnoporus coccineus (white rot) | Face grain | 15 | 12 | 465 (54) |
20 | 13 | 451 (41) | ||
25 | 13 | 463 (58) | ||
End grain | 15 | 16 | 473 (37) | |
20 | 18 | 458 (49) | ||
25 | 20 | 464 (40) |
2.2 Fungal inoculation
2.3 Mechanical tests
2.4 Comparison with design codes
2.5 Statistical analysis
Source | Predicted SWC | Formula | |
---|---|---|---|
AS 1720.1 (Standards Australia 2010) | \({N}_{k,j}\) | \({N_{k,j}} = {k_{13}}{l_p}n{Q_k}\) k13 =1.0 for face grain;0.6 for end grain lp =depth of screw penetration = 20 mm n =number of screws = 1 Qk =characteristic capacity = 51 N/mm | (Eq. 1) |
EC5 (CEN 2004) | \({F}_{ax,\alpha ,Rk}\) | \({F}_{ax,\alpha ,Rk}=\frac{{n}_{ef} {f}_{ax,k} d {l}_{ef} }{{1.2cos}^{2}\alpha + {sin}^{2}\alpha }{\left(\frac{{\rho }_{k}}{{\rho }_{a}}\right)}^{0.8}\) nef = effective number of screws = 1 \({f_{ax,k}} = 0.52{d^{ - 0.5}}le{f^{ - 0.1}}\rho {{\rm{k}}^{0.8}}\) d = shank diameter = 3.84 mm lef =depth of screw penetration = 20 mm 𝝆k = characteristic density = 5th percentile of the batch 𝝆a = associated density = 419 kg/m3 α = angle between the screw axis and grain direction | (Eq. 2) |
USDA (Rammer 2010) | \(P\) | \(P=108.25{G}^{2}DL\) G = specific gravity of wood at 12% MC D = screw shank diameter = 3.84 mm L = depth of screw penetration = 20 mm | (Eq. 3) |
3 Results and discussion
3.1 Effects of wetting-sterilization on the screw withdrawal capacity
3.1.1 Sterilized specimens
3.1.2 Decayed specimens
Sample | Exposed time (weeks) | Screw on | ρf (kg/m3) | mass loss (wt %) | SWC (kN) |
---|---|---|---|---|---|
Control | 0 | Face grain | - | - | 1.38 (0.49) |
End grain | - | - | 1.07 (0.40) | ||
Sterilized | 0 | Face grain | 522 (35) | 0.1 (0.1) | 1.49 (0.20) |
25 | 518 (36) | 1.1 (0.2) | 2.17 (0.18) | ||
0 | End grain | 502 (4) | 0.5 (0.1) | 1.75 (0.21) | |
25 | 462 (33) | 0.6 (0.3) | 1.46 (0.33) | ||
Brown rot | 15 | Face grain | 390 (45) | 17.7 (2.4) | 0.42 (0.12) |
20 | 367 (25) | 22.8 (2.4) | 0.42 (0.09) | ||
25 | 360 (42) | 27.6 (3.5) | 0.26 (0.06) | ||
15 | End grain | 376 (20) | 18.4 (2.5) | 0.49 (0.15) | |
20 | 391 (41) | 22.4 (2.4) | 0.51 (0.11) | ||
25 | 351 (26) | 29.4 (4.3) | 0.33 (0.11) | ||
White rot | 15 | Face grain | 417 (54) | 7.9 (1.5) | 1.13 (0.34) |
20 | 390 (42) | 11.8 (1.5) | 1.16 (0.27) | ||
25 | 403 (57) | 11.8 (3.0) | 1.13 (0.25) | ||
15 | End grain | 420 (36) | 8.5 (3.0) | 1.07 (0.12) | |
20 | 403 (48) | 10.0 (1.2) | 1.10 (0.21) | ||
25 | 412 (38) | 10.6 (2.5) | 1.02 (0.16) |